ZoomActivity.java

/*
 * Copyright 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.animationsdemo;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.content.Intent;
import android.graphics.Point;
import android.graphics.Rect;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.NavUtils;
import android.view.MenuItem;
import android.view.View;
import android.view.animation.DecelerateInterpolator;
import android.widget.ImageView;

/**
 * A sample showing how to zoom an image thumbnail to full-screen, by animating the bounds of the
 * zoomed image from the thumbnail bounds to the screen bounds.
 *
 * <p>In this sample, the user can touch one of two images. Touching an image zooms it in, covering
 * the entire activity content area. Touching the zoomed-in image hides it.</p>
 */
public class ZoomActivity extends FragmentActivity {
    /**
     * Hold a reference to the current animator, so that it can be canceled mid-way.
     */
    private Animator mCurrentAnimator;

    /**
     * The system "short" animation time duration, in milliseconds. This duration is ideal for
     * subtle animations or animations that occur very frequently.
     */
    private int mShortAnimationDuration;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_zoom);

        // Hook up clicks on the thumbnail views.

        final View thumb1View = findViewById(R.id.thumb_button_1);
        thumb1View.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoomImageFromThumb(thumb1View, R.drawable.image1);
            }
        });

        final View thumb2View = findViewById(R.id.thumb_button_2);
        thumb2View.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoomImageFromThumb(thumb2View, R.drawable.image2);
            }
        });

        // Retrieve and cache the system's default "short" animation time.
        mShortAnimationDuration = getResources().getInteger(android.R.integer.config_shortAnimTime);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                // Navigate "up" the demo structure to the launchpad activity.
                // See http://developer.android.com/design/patterns/navigation.html for more.
                NavUtils.navigateUpTo(this, new Intent(this, MainActivity.class));
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * "Zooms" in a thumbnail view by assigning the high resolution image to a hidden "zoomed-in"
     * image view and animating its bounds to fit the entire activity content area. More
     * specifically:
     *
     * <ol>
     *   <li>Assign the high-res image to the hidden "zoomed-in" (expanded) image view.</li>
     *   <li>Calculate the starting and ending bounds for the expanded view.</li>
     *   <li>Animate each of four positioning/sizing properties (X, Y, SCALE_X, SCALE_Y)
     *       simultaneously, from the starting bounds to the ending bounds.</li>
     *   <li>Zoom back out by running the reverse animation on click.</li>
     * </ol>
     *
     * @param thumbView  The thumbnail view to zoom in.
     * @param imageResId The high-resolution version of the image represented by the thumbnail.
     */
    private void zoomImageFromThumb(final View thumbView, int imageResId) {
        // If there's an animation in progress, cancel it immediately and proceed with this one.
        if (mCurrentAnimator != null) {
            mCurrentAnimator.cancel();
        }

        // Load the high-resolution "zoomed-in" image.
        final ImageView expandedImageView = (ImageView) findViewById(R.id.expanded_image);
        expandedImageView.setImageResource(imageResId);

        // Calculate the starting and ending bounds for the zoomed-in image. This step
        // involves lots of math. Yay, math.
        final Rect startBounds = new Rect();
        final Rect finalBounds = new Rect();
        final Point globalOffset = new Point();

        // The start bounds are the global visible rectangle of the thumbnail, and the
        // final bounds are the global visible rectangle of the container view. Also
        // set the container view's offset as the origin for the bounds, since that's
        // the origin for the positioning animation properties (X, Y).
        thumbView.getGlobalVisibleRect(startBounds);
        findViewById(R.id.container).getGlobalVisibleRect(finalBounds, globalOffset);
        startBounds.offset(-globalOffset.x, -globalOffset.y);
        finalBounds.offset(-globalOffset.x, -globalOffset.y);

        // Adjust the start bounds to be the same aspect ratio as the final bounds using the
        // "center crop" technique. This prevents undesirable stretching during the animation.
        // Also calculate the start scaling factor (the end scaling factor is always 1.0).
        float startScale;
        if ((float) finalBounds.width() / finalBounds.height()
                > (float) startBounds.width() / startBounds.height()) {
            // Extend start bounds horizontally
            startScale = (float) startBounds.height() / finalBounds.height();
            float startWidth = startScale * finalBounds.width();
            float deltaWidth = (startWidth - startBounds.width()) / 2;
            startBounds.left -= deltaWidth;
            startBounds.right += deltaWidth;
        } else {
            // Extend start bounds vertically
            startScale = (float) startBounds.width() / finalBounds.width();
            float startHeight = startScale * finalBounds.height();
            float deltaHeight = (startHeight - startBounds.height()) / 2;
            startBounds.top -= deltaHeight;
            startBounds.bottom += deltaHeight;
        }

        // Hide the thumbnail and show the zoomed-in view. When the animation begins,
        // it will position the zoomed-in view in the place of the thumbnail.
        thumbView.setAlpha(0f);
        expandedImageView.setVisibility(View.VISIBLE);

        // Set the pivot point for SCALE_X and SCALE_Y transformations to the top-left corner of
        // the zoomed-in view (the default is the center of the view).
        expandedImageView.setPivotX(0f);
        expandedImageView.setPivotY(0f);

        // Construct and run the parallel animation of the four translation and scale properties
        // (X, Y, SCALE_X, and SCALE_Y).
        AnimatorSet set = new AnimatorSet();
        set
                .play(ObjectAnimator.ofFloat(expandedImageView, View.X, startBounds.left,
                        finalBounds.left))
                .with(ObjectAnimator.ofFloat(expandedImageView, View.Y, startBounds.top,
                        finalBounds.top))
                .with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_X, startScale, 1f))
                .with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_Y, startScale, 1f));
        set.setDuration(mShortAnimationDuration);
        set.setInterpolator(new DecelerateInterpolator());
        set.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                mCurrentAnimator = null;
            }

            @Override
            public void onAnimationCancel(Animator animation) {
                mCurrentAnimator = null;
            }
        });
        set.start();
        mCurrentAnimator = set;

        // Upon clicking the zoomed-in image, it should zoom back down to the original bounds
        // and show the thumbnail instead of the expanded image.
        final float startScaleFinal = startScale;
        expandedImageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (mCurrentAnimator != null) {
                    mCurrentAnimator.cancel();
                }

                // Animate the four positioning/sizing properties in parallel, back to their
                // original values.
                AnimatorSet set = new AnimatorSet();
                set
                        .play(ObjectAnimator.ofFloat(expandedImageView, View.X, startBounds.left))
                        .with(ObjectAnimator.ofFloat(expandedImageView, View.Y, startBounds.top))
                        .with(ObjectAnimator
                                .ofFloat(expandedImageView, View.SCALE_X, startScaleFinal))
                        .with(ObjectAnimator
                                .ofFloat(expandedImageView, View.SCALE_Y, startScaleFinal));
                set.setDuration(mShortAnimationDuration);
                set.setInterpolator(new DecelerateInterpolator());
                set.addListener(new AnimatorListenerAdapter() {
                    @Override
                    public void onAnimationEnd(Animator animation) {
                        thumbView.setAlpha(1f);
                        expandedImageView.setVisibility(View.GONE);
                        mCurrentAnimator = null;
                    }

                    @Override
                    public void onAnimationCancel(Animator animation) {
                        thumbView.setAlpha(1f);
                        expandedImageView.setVisibility(View.GONE);
                        mCurrentAnimator = null;
                    }
                });
                set.start();
                mCurrentAnimator = set;
            }
        });
    }
}